Process for treating acrylonitrile fibers with ultra-violet light stabilizer



United States Patent 3 281,260 PROCESS FOR TREATING ACRYLONITRILE FIBERS WITH ULTRA-VIOLET LIGHT STA- BILIZER Pompelio A. Ucci, Decatur, Ala., assignor to Monsanto Company, a corporation of Delaware No Drawing. Filed Nov. 19, 1962, Ser. No. 238,736 9 Claims. (Cl. 11733.3)

This invention relates to a method for improving the heat and light stability during the spinning, subsequent processing and use of a synthetic linear fiber. More specifically, this invention is concerned with a method of producing acrylic fibers which are stable to heat and light degradation not only during the spinning process but also through subsequent normal usage such as dyeing, texturizing and bleaching.

According to experience and knowledge of the prior art, there is a natural instability of synthetic linear fibers to ultra-violet light which reduces the lightness and purity of these fibers. This is especially true concerning the acrylic fibers or those fibers which contain a predominant amount of acrylonitrile in the fiber. This instability is especially true concerning these acrylic fibers whch have been subjected to a bleachng operation and then exposed to ultra-violet light which of course is part of natural daylight. This action may be explained, it is thought, by the assumption that oxygen which is gene-rated by these bleaching compositions tends to become activated when exposed to ultra-violet light and causes some discoloration of the fibers. This slight attack on the fibers generally results in a darkening of the fibers thus resulting in an inability of using these fibers for the production of yarns, fabrics, etc., in which there is desired a natural white or a colorless fiber, or even where light pastel colors or shades are desired. Any treatment or method of treatment which will result in an improvement in the stability of the acrylic fibers is most welcomed in the synthetic fiber industry.

An object of this invention is to provide a method for tabilizing synthetic linear fibers against degradation due to normal sunlight.

Another object of this invention is to provide a method for improving the color and light stability of acrylic yarns or fibers.

Another object of this invention is to provide a method for improving the color and light stability of fibers or yarns composed of at least 80 percent acrylonitrile and up to 20 percent of another mono-olefinic copolymerizable monomer.

Another object of this invention is to provide a method for the improvement in color and light stability of fibers composed of 94 percent acrylonitrile and 6 percent vinyl acetate.

Another object of this invention is to provide a method for improving the color and light stability of fibers composed of a blend of two copolymers, 88 percent of the first copolymer being 94 percent acrylonitrile and 6 percent vinyl acetate, and 12 percent of the second copolymer being 50 percent acrylonitrile and 50 percent methylvinypyridine.

Another object of this invention is to provide a method for the improvement in color and light stability of bleached acrylic fibers against ultra-violet light degradation.

' Other objectives and advantages ancillary to the principal object that may be realized by the practice of this invention are manifest in the ensuing description and specification.

Generally the objects of this invention are accomplished by treating the fiber during its spinning operation and while it is still in the gel state with a metallic salt of 3,281,260 Patented Oct. 25, 1966 the naphthalene disulfonic acids or the naphthalene disulfonic acids alone.

More specifically, the objects of this invention are obtained by treating the acrylic fibers as they are spun through a conventional spinning operation and are still in the gel state with an additive which is one of the naphthalene disulfonic acids or the alkali metal salts of the naphthalene disulfonic acids. These salts are for example; the sodium salt of 1,5, naphthalene disulfonic acid, the potassium salt of 1,5, naphthalene disulfonic acid, or any of the alkali metal salts of any of the naphthalene disulfonic acids such as in addition to 1,5, naphthalene disulfonic acid, 1,3, naphthalene disulfom'c acid, 1,2, naphthalene disulfonic acid, 1,6, naphthalene disulfonic 1,7, naphtha-lene disulfonic acid etc. The amount of this metallic salt or the acid itself which may be used or added to fibers may vary from .001 percent to 5 percent based upon the weight of the fiber with the preferred amount being 0.1 percent based upon the weight of the fiber. The conventional methods of spinning of acrylic fibers are well known in the art and are not germane to this present invention except that these stabilizing additives are applied to the fibers during this conventional spinning process while the fiber is still in the gel state.

While this application has been generally directed to synthetic fibers, it is especially useful in the stabilizing of fibers composed of acrylic polymers. The polymeric materials, which may be employed in the practice of the present invention, are polyacrylonitrile, copolymers, including binary and ternary polymers containing at least percent by weight of acrylonitrile in the polymer molecule, or a blend comprising polya-crylonitrile or copolymers comprising acrylonitrile with from 2 percent to 50 percent of another polymeric material, the blend having an overall polymerized acrylonitrile content of at least 80 percent by weight. While the preferred polymers employed in the instant invention are those con-v taining at least 80 percent of'acrylonitrile, generally recognized as the fiber forming acrylonitrile polymers, it will be understood that the invention is likewise applicable to polymers containing less than 80 percent acrylonitrile. The acrylonitrile polymers containing less than 80 percent aorylonitrile are useful in forming film, coating compositions, molding operations, lacquers and also in forming the modacrylic fibers.

For example, the polymer may be a copolymer of from 80 percent to 98 percent acrylonitrile and of from 2 percent to 20 percent of another monomer containing the C =C linkage and copolymerizable with acrylonit-rile. Suitable mono-olefinc monomers include acrylic, aipha-chloroacrylic and methacrylic acid; the acrylates, such as methylrnJe-thacrylate, ethylmethacrylate, butylmethacrylate, methoxymethyl methacrylate, beta-chloroethyl mlethacrylate and the corresponding esters of acrylic and alpha-chloroacrylic acids; vinyl chloride, vinyl fiuorride, vinyl bromide, vinylidene chloride, l-chloro-l-bromoethylene; methacrylonitrile; acrylamide and methacrylamide; alpha-chloro-acrylamide; or monoalkyl substituted products thereof; methylvinylketone; vinylcarboxylate-s such as vinyl acetate, vinyl chloroacetate, vinyl propionate, and vinyl stearate; N-vinylimides such as N-vinylphthalimide and N-vinylsuccinimlide; methylene malonic ester; itaconic acid and itaconic esters; N-vinylcarbazoles; vinyl furane; alkyl vinyl esters; vinyl sulfonic acid; ethylene alpha, beta-dicarhoxylic acids or their anhydrides or derivatives, such as diethylcitraconate, diethylmesaconate, styrene, vinyl naphthalene; vinyl-substituted tertiary heterocyclic amines, such as the vinylpyridines and alkylsubstituted vinylpyridines, for example, Z-Vinylpyridine, 4-vinylpy-ridine, 2-me-thyl-5-vinylpyridine, 'etc.; l-vinylto 98 percent of acrylonitrile, firom 1 percent to 10 percent of a vinylpyridine or a l-vinylitmidazole, and from 1 percent to 18 percent of another substance such as methacrylonitrile or vinyl chloride.

The polymer may also be a blend of a polyacrylonitrile or of a binary interpolymer of from 80 percent to 99 percent acrylonitrile and from 1 percent to 20 percent of at least one other C=C containing substance with from 2 percent to 50 percent of the weight of the blend of a copolymer of from 10 percent to 70 percent of acrylonitrile and from 30 percent to 90 percent of at least one other C=C containing polymerizable monomer. Preferably, when the polymeric material comprises a blend, it will be a blend of a copolymer of 90 percent to 98 percent acrylonitrile and from 2 percent to 10 percent of another mono-olefinic monomer, such as vinyl acetate, with sufficient amount of copolymer of from 10 percent to 70 percent of acrylonitrile and from 30 percent to 90 percent of a vinyl-substituted tertiary heterocycli'c amine, such as vinylpyridine or l-vinylirnidazole, to give a dyeable blend having an overall vinyl-substituted tertiary heterocyclic amine content of from 2 percent to 10 percent, based on the weight of the blend.

The following examples are cited to illustrate the invention. They are not intended to limit it in any way. Unless otherwise noted, percentages as expressed in the examples indicate percent by weight.

Example 1 A dope composed of 94 percent acrylonitrile and 6 percent vinyl acetate and a conventional solvent was extruded into a conventional coagulating bath composed of water and solvent in filamentary form, stretched, washed and before drying then passed through a conventional finish bath composed of the usual lubricating agents, anti-static agents, softening agents; anti-soiling agents, etc., and 0.1 percent, based upon the weight of the fiber, of 1,5, naphthalene disulfonic acid. The fibers were then dried and passed through the conventional textile machinery. The fibers were then subjected to testing by a recording spectrophotometer, made by General Electric Company. The fibers prior to being tested by the spectrophotometer was subjected to bleaching with a chlorite. The fibers after bleaching were then divided into two parts, the first part being exposed to ultra-violet light and the second part remaining unexposed. After being checked with the spectrophotometer concerning lightness, it was found that the fibers exposed to ultra-violet light had a lightness of 82.6 and the part of the fibers which were not exposed .to ultraviolet light had a lightness of 89.7. The fibers exposed to ultra-violet light had a purity of 7.8 and the fibers which were not exposed to ultra-violet light had a purity of 1.6. These readings were compared to fibers which were spun under normal conditions but did not have the special additive in the finish bath. The lightness of the control fiber which had been exposed to ultra-violet light was 78.6 and the fibers which were not exposed to ultraviolet light had a lightness of 87.6. The fibers which were exposed to ultra-violet light had a purity of 9.1 and those fibers unexposed to ultra-violet light had a purity of 1.6. Thus the fiber-s which were treated with the special additive in the finish bath and which had been bleached and both exposed and unexposed to ultra-violet light, possessed a marked improvement in lightness over the control fibers which had not had'this special stabilizing additive in their finish bath.

Example 2 A dope composed of 94 percent acrylonitrile and 6 percent vinyl acetate and a conventional solvent was extruded into a conventional coagulating bath as in Example 1 and the stabilizing additive 1,5, naphthalene disulfonic acid was placed in this finish bath. This additive amounted to 0.1 percent by weight of the fiber. These fibers were not bleached and were divided into two parts, one being subjected to ultra-violet light and the second part being unexposed to ultra-violet light. The fibers were then tested in the recording spectrophotometer, manufactured by General Electric Company, and it was determined that the fibers which had been exposed to ultra-violet light had a lightness of 84. 9 and the fibers unexposed to ultra-violet light had a lightness of 83.7. The fibers which had been exposed to ultra-violet light had a purity of 4.4 and the fibers which were unexposed to ultra-violet light had a purity of 5.6. These readings were compared to a control sample which was unbleached and also had no special stabilizing additive. The control samples which were unexposed to ultra-violet light showed a lightness of 81.6 and the fibers which were exposed to ultra-violet light of the control sample had a lightness of 82.2. The control fibers which were exposed to ultra-violet light had a purity of 5.8 and the fibers which were unexposed to ultra-violet light had a purity of 7.1. Thus it is seen that the fibers which were unbleached and had the special stabilizing additive added to their finish bath showed a marked improvement over the control fibers concerning their lightness and purity whether they were exposed to their ultra-violet light or were not exposed to ultra-violet light.

Thus it is seen by the method of the present invention through the use of the stabilizing additive that acrylic fibers produced by any conventional spinning method showed a marked improvement in their stability to ultraviolet light as to their lightness and purity. This is true concerning both the unbleached fibers and the bleached fibers when they have been treated with the special stabilizing additive while still in the gel state. This will aid greatly in permitting the use of these acrylic fibers in manufacturing yarns of natural color or yarns which will be dyed with the light pastel shades.

It is understood that changes and variations may be made in the present invention by one skilled in the art without departing from the spirit and scope thereof as defined in the appended claims.

I claim:

1. A method for stabilizing synthetic linear fibers against ultra-violet light comprising treating said fibers during their spinning with a member selected from the group consisting of the naphthalene disulfonic acids and the alkali metal salts of the naphthalene disulfonic acids.

2. A method for stabilizing acrylic fibers against degradation due to ultra-violet light comprising treating said fibers with a: member selected from the group consisting of the naphthalene disulfonic acids and the alkali metal salts of the naphthalene disulfonic acids during their spin- IllIlg operation.

3. A method for stabilizing fibers composed of at least percent acrylonitr-ile and up to 20 percent of another mono-olefinic monomer copolymerizable therewith against degradation due to ultra-violet light, comprising treating said fiber with a member selected from the group consisting of the naphthalene disulfonic acids and the alkali metal salts of the naphthalene disulfonic acids during their spinning operation.

4. A method for stabilizing fibers composed of 94 percent acrylonitrile and 6 percent vinyl acetate against degradation due to ultra-violet light comprising treating said fibers with a member selected from the group consisting of the naphthalene disulfonic acids and the alkali metal salts of the naphthalene disulfonic acids during their spinning operation.

5. A method for stabilizing fibers composed of a blend of two copolymers, 88 percent of the first copolymer being 94 percent acrylonitrile and 6 percent vinyl acetate and 12 percent of the second copolymer being 50 percent acrylonitrile and 50 percent methyl vinylpyridine, against degradation due to ultra-violet light comprising treating said fibers with a member selected from the group consisting of the naphthalene disulfonic acids and the alkali metal salts of the naphthalene disul-fonic acids during their spinning operation.

6. A method of stabilizing fibers composed of at least 80 percent acrylonitrile and up to 20 percent of another mono-olefinic monomer copolymerizable therewith, against degradation due to ultra-violet light, comprising treating the fibers while said fibers are in a gel state with a member selected from the group consisting of naphthalene disulfonic acids and the alkali metal salts of the naphthalene disulfonic acids varying from 0.001 percent to 5 percent, based upon the weight of the fiber.

7. A method for stabilizing fibers composed of 94 percent acrylonitrile and 6 percent vinyl acetate against degradation due to ultra-violet light, comprising treating said fibers during their spinning operation with 0.01 percent of 1,5, naphthalene disulfonic acid.

8. A method for stabilizing fibers composed of a blend of two copolymers, 88 percent of the first copolymer be- References Cited by the Examiner UNITED STATES PATENTS 2,210,962 8/1940 Thomas 260-505 2,423,972 7/1947 Gluesenka-mp et al.

117-1395 X 2,597,708 5/ 1952 Cresswell. 2,614,289 10/1952 Cresswell 117139.5 X 2,626,876 1/1953 Carries 117138.8 2,626,877 1/1953 Carnes 117-138.8 3,095,422 6/1963 Duennenberger et a1.

3,160,665 12/1964 Siegrist et a1. 252300 X WILLIAM D. MARTIN, Primary Examiner.

T. G. DAVIS, Assistant Examiner. 

1. A METHOD FOR STABILIZING SYNTHETIC LINEAR FIBERS AGAINST ULTRA-VIOLET LIGHT COMPRISING TREATING SAID FIBERS DURING THEIR SPINNING WITH A MEMBER SELECTED FROM THE GROUP CONSISTING OF THE NAPHTHALENE DISULFONIC ACIDS AND THE ALKALI METAL SALTS OF THE NAPHTHALENE DISULFONIC ACIDS. 